Browsing by Author "Babu, N.N."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    High Velocity Air Fuel Spraying for Surface Restoration of Worn-out IN718
    (Springer, 2025) Sreerag, M.P.; Abhijith Vijay, V.; Babu, N.N.; Ali, S.S.; Cadambi, S.; Rajasekaran, B.
    This study explores the efficacy of high velocity air fuel (HVAF) spraying for repairing worn-out IN718 thrust collars used in the chemical industry. We investigated the characteristics and application potential of thick IN718 depositions for surface restoration, focusing on their adhesion. To evaluate microstructure and adhesion, approximately 2-mm-thick IN718 layers were deposited onto IN718 wrought coupons. The HVAF-sprayed layers were notably dense (99.5%) and exhibited excellent hardness, reaching 450 HV0.3, which suggests superior mechanical properties compared to the bulk material. A three-point bending test was conducted to assess the adhesion strength of these thick deposits. The results demonstrated excellent adhesion in both compressive (1281 MPa with > 2% strain) and tensile bending. Trusting in these promising substrate-layer interfacial adhesion characteristics, the investigation was extended to demonstrate the refurbishment of an actual worn-out industrial IN718 thrust collar. A 2-mm-thick IN718 deposition was applied to the entire worn area, and excess material was subsequently machined to achieve the desired surface finish for reuse. Overall, HVAF spray technology shows significant promise for developing thick metallic layers with excellent interfacial adhesion, providing a robust and viable solution for effectively refurbishing heavily worn metallic components and extending their service life. © ASM International 2025.
  • No Thumbnail Available
    Item
    Microstructural, Mechanical, and Tribological Evaluation of HVAF-Sprayed Inconel 718 Coatings
    (Springer, 2025) Babu, N.N.; Kumar, S.; Cadambi, S.
    This study evaluates the mechanical and wear properties of IN718 coating on IN625 substrates deposited using the HVAF-spraying technique. The deposited coating was characterized by SEM, EDS, EBSD, Raman, nanoindentation, and microhardness. The integrity and adhesion of the coating were assessed using scratch tests aided by acoustic emission spectroscopy. The tribological evaluation was performed using a dry sliding wear test with a ball-on-coated disc configuration using alumina as the counterface. The coating microstructure comprises mostly unmelted particles with a small fraction of melted, with a porosity level < 1.5% and about 8.4% oxidation. Both the microhardness and nanoindentation show the anisotropy in the coating. The elastic modulus is at the same level as bulk IN718 when measured perpendicularly to the thickness direction, but it is lower when measured along the thickness. The average compressive stress of 608 MPa and the Bauschinger effect influence the anisotropy observed in the coatings. ISO 27307 scratch tests reveal that coatings have good cohesion and adhesion strength. Wear tests were performed at room temperature, 400 °C and 600 °C. The room temperature wear is high and abrasive, while the high-temperature wear was lower and determined to be oxidative. Porosity is detrimental to the abrasive wear at room temperatures, which leads to localized chipping. © ASM International 2025.